Reference control data obtained from an in vivo comet-micronucleus combination assay using Sprague Dawley rats

Area of Science:

• Toxicology
• Genetics
• Pharmacology

Background:

• International Conference on Harmonization (ICH) S2(R1) guidelines require in vivo follow-up for positive in vitro genotoxicity tests.
• The in vivo alkaline comet assay and erythrocyte micronucleus test are key components of genotoxicity assessment.
• Combining assays improves efficiency and animal welfare compared to separate tests.

Purpose of the Study:

• To validate a protocol for a combined in vivo comet-micronucleus assay in rats.
• To establish the appropriate dose for the positive control, ethyl methanesulfonate (EMS).
• To assess the assay's performance using both negative (vehicle) and positive (EMS) controls.

Main Methods:

• A combination assay protocol was developed and validated in male Sprague Dawley rats.
• Three daily administrations of the test substance were used.
• Data were collected for comet assays (liver, stomach, kidney) and micronucleus assays (bone marrow).

Main Results:

• Negative control data aligned with historical control data from standalone assays.
• Positive control (ethyl methanesulfonate) demonstrated clear and consistent genotoxic effects in both comet and micronucleus assays.
• The validated assay protocol showed reliable performance for both endpoints.

Conclusions:

• The in vivo comet-micronucleus combination assay is a validated and effective method for genotoxicity testing.
• This combined approach meets regulatory requirements and enhances animal welfare.
• The assay provides a robust platform for detecting a broad spectrum of DNA damage.